The present invention is directed to the integration of organic light emitting devices of different colors onto a common substrate.
Organic light emitting devices (OLEDs) are light emitting devices that are comprised of several layers, in which one of the layers is comprised of an organic material that can be made to electroluminesce by applying a voltage across the device. A long sought goal in the display field has been the integration of light emitting devices (LEDs) of three different colors onto a single substrate. While OLEDs have shown versatility in terms of colors and freedom of substrates in recent years, integration of OLEDs of different colors has proven difficult because of difficulties associated with the. processing and patterning of the organic materials. Therefore, multicolor work to date in the field has been based on integrating red, green and blue filters over a single type of white emitting device, integrating red and green down-conversion phosphors with a single type of blue emitting device, or adjusting the emission of a single type of broadband organic emitter by using three different kinds of microcavities.
A clearly desirable alternative would be to fabricate three different devices with three different organic layers, each optimized for a different color and integrated onto a common substrate. However, there are difficulties associated with the integration of red, green and blue devices for the subpixels of a full-color display. For example, the microfabrication of small pixels in high resolution displays will involve the patterning of films and microprocessing, which inevitably require the use of solvents, acid and water. The direct exposure of organic materials to solvents, acid and water can lead to the degradation or even the complete failure of devices. For instance, the solvent carrying polymers during later spin-coating of another layer might redissolve the polymer thin films in existing devices. Therefore, a need exists to integrate multiple organic LEDs on a single substrate with each LED representing a different color without degrading the devices.
The present invention is directed to OLED device structures and methods that allow for multiple colors to be integrated onto a single substrate.
An advantage of the present invention is that OLEDs for multiple colors can be integrated on a single substrate without substantial device degradation.
Several embodiments of the invention are directed to an organic light emitting device. The device comprises: a substrate, a first electrical contact layer over the substrate, a patterned organic layer over the first contact layer, a second electrical contact layer over the organic layer, and a covering portion covering the sides of the organic layer. The first electrical contact layer can be patterned.
In a first related embodiment, the covering portion includes an insulating sidewall extending from the first electrical contact layer to the second electrical contact layer.
In a second related embodiment, the first electrical contact layer is patterned, the organic layer covers sides of the first electrical contact layer, and the covering portion includes a conductive layer extending at least from the substrate to the second electrical contact layer.
In third and fourth related embodiments, the device further comprises an insulating layer with an aperture formed therein over the first electrical contact layer. The organic layer extends over and into the aperture and a over portion of the insulating layer adjacent the aperture. In the third related embodiment, the covering portion includes a conductive layer extending from the insulating layer and covering the second electrical contact layer. In the fourth related embodiment, the covering portion includes a conductive or insulating sidewall extending from the insulating layer to the second electrical contact layer.
In the above embodiments, the following materials are among those preferred: A preferred substrate material for the practice of the present invention is glass. Preferred insulating layer materials and insulating covering portions (including sidewall spacers and covering layers) include silicon dioxide, silicon nitride, silicon oxynitride, and various insoluble organic materials. Preferred conducting covering portions include aluminum. Depending on the application, the first electrical contact can be the anode or the cathode, with the second electrical contact being the converse. Anode materials preferred for the practice of the present invention include platinum as well as indium-tin oxide or other transparent conducting oxide materials. A preferred cathode construction for the practice of the present invention is an Mg:Ag alloy overcoated with Ag. A preferred organic layer is a molecularly doped polymer such as a hole-transporting matrix polymer doped with one or more electron transporting molecules and one or more dyes. Preferred hole-transporting matrix polymers include PVK (poly[N-vinylcarbazole]). Preferred electron transporting molecules include tris(8-hydroxy quinolate)aluminum (Alq) and 2-(4-biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD). Another preferred class of organic materials includes conjugated polymers, such as polyphenylene vinylene and its derivatives (including MEHPPV). Of course, a host of other materials/configurations will readily suggest themselves to those skilled in the art.
It is contemplated that the above devices may be incorporated into computers, televisions, billboards, signs, vehicles, printers, telecommunications devices, telephones, and copiers.
Other embodiments of the invention are directed to a method of forming an organic light emitting device. The method comprises providing a first electrical contact layer, providing a first organic layer or layers over the first electrical contact layer, providing a patterned second electrical contact layer over the first organic layer, and etching the first organic layer using the patterned second electrical contact layer as a mask. In an alternative embodiment, the first organic layer is etched using as a mask a layer on top of the patterned second electrical contact layer which has the same pattern as the patterned second electrical contact layer. The first electrical contact layer may be patterned before providing the first organic layer. The first organic layer is preferably provided by spin coating or vacuum deposition. The second electrical contact layer is preferably patterned using a shadow mask technique or a photoresist technique.
In one embodiment, the step of etching exposes an area over the first electrical contact layer. A second organic layer is preferably provided over the exposed area, followed by an additional conductive layer and an additional etch step.
Many additional embodiments will become apparent upon reading the present specification and claims.